First when emails are sent they are stored somewhere, so if you are to track the email, you will most likely track to the web server they are stored on or sent from.
In the email you can click most times to view raw source. And under their you will see a host of text. Start looking for "received: from" Their you will see a bunch of ip's. I would recommend looking up those ip's to rule out the ones that are like a google server or other. Hope this helps.